In the automobile industry, heat exchangers, such as those used for engine cooling, are manufactured in high volume and must meet the requirements of reliability and low cost. Additionally, the heat exchanger should be adaptable in design so that it can be installed in available installation space in a particular vehicle. A typical automotive heat exchanger comprises a pair of manifolds or headers with a plurality of tubes extending between the manifolds for conveying cooling fluid between the manifolds. Heat radiating fins are secured between the tubes to promote heat transfer to the surrounding atmosphere. Inlet and outlet pipes are connected to the manifolds for circulation of the engine cooling fluid through the heat exchanger. Mounting brackets for the heat exchanger are also connected with the manifolds.
The components of the heat exchanger are typically made from aluminum. For each two components which are to form a water-tight joint, at least one of said components must be provided with a cladding of brazing material for sealing both said components together in final assembly. The manifolds are typically formed from aluminum sheet which is rolled to form a pipe with the edges joined together.
For connecting the plurality of tubes to the manifolds, a plurality of slots are provided in the manifolds and the tubes are inserted into the slots. The fins are positioned between the tubes. End caps are placed over the ends of the manifolds and the inlet and outlet pipes are positioned in openings in the manifolds. The components of the heat exchanger described above are held and properly positioned in a provisional assembly by suitable fixtures. The provisional assembly is then heated in a brazing furnace to provide a final assembly with permanent joints between all said heat exchanger components and the manifolds.
In the prior art, it is common practice to make heat exchangers with one-piece manifolds wherein each manifold is formed from sheet metal with the longitudinal edges of the sheet stock being joined together to form a pipe. This is disclosed in the Nobusue et al. U.S. Pat. No. 4,945,635 granted Aug. 7, 1990 and the Kobayashi et al. U.S. Pat. No. 5,243,842 granted Sep. 14, 1993. Both of these patents disclose the use of sheet aluminum with a cladding of brazeable material.
Other patents which disclose heat exchangers including one-piece manifolds are: Rhodes et al. U.S. Pat. No. 5,743,122, granted Apr. 28, 1998; Shinmura et al. U.S. Pat. No. 5,172,762, granted Dec. 22, 1992; Hutto et al. U.S. Pat. No. 5,481,800, granted Jan. 9, 1996; Ando U.S. Pat. No. 5,082,051, granted Jan. 21, 1992; Aoki patent U.S. Pat. No. 5,214,847 granted Jun. 1, 1993; and Kato patent U.S. Pat. No. 5,558,159 granted Sep. 24, 1996. Of these, Rhodes et al. describes a circular manifold with a brazed butt joint. The Shinmura et al. patent and the Hutto et al. patent both disclose a lap joint in a cylindrical manifold. The Shinmura et al. patent discloses a one-piece manifold of rectangular configuration with an interlock joint of the longitudinal edges.
The prior art also discloses joining of a pipe or tube into the sidewall of a larger pipe or tube with soldering or brazing of the pipes. The Kushner et al. U.S. Pat. No. 3,971,500 granted Jul. 27, 1976 discloses a heat exchanger with a small cylindrical tube joined to the wall of a larger cylindrical tube by a solder connection. The small tube is formed with an annular rib and the free end is inserted into a circular opening in the larger tube. Both tubes are provided with a cladding of solder and are heated to reflow the solder to join the tubes together. The Hingorany U.S. Pat. No. 3,750,747 granted Aug. 5, 1973 discloses attachment of a metal plate with a solder cladding to an unclad tube by heating the parts to solder them together.
Also in the prior art is a manifold for a heat exchanger as shown in FIG. 3. This manifold comprises a plastic molded tank A which has a flat rim B on the top of the walls and also has pipes C attached. A manifold panel D is formed from sheet metal as a flat panel with unitary attachment flanges E extending from all sides of the panel. A sealing gasket F is disposed between the rim of the tank and the bottom surface of the panel. After the flat tubes (not shown) are brazed to the manifold panel D, the attachment flanges E are crimped around the rim B to clamp the gasket F between the rim and panel.